Whirling tool

ABSTRACT

A whirling tool for machining a workpiece, having: three or a multiple of three cutting plates, wherein each of the cutting plates comprises at least one cutting edge; a cutting plate holder having a plurality of cutting plate receptacles, wherein each of the cutting plate receptacles is configured to receive one of the cutting plates, wherein the cutting plate receptacles are disposed so as to be distributed in a circumferential direction across the cutting plate holder; and a plurality of fastening elements for releasably fastening the cutting plates in the cutting plate receptacles of the cutting plate holder; wherein the cutting plates comprise at least two different kinds of cutting plates, wherein at least one cutting plate of a first kind, and one cutting plate of a second kind are provided for each group of three cutting plates that are disposed beside one another on the cutting plate holder, wherein the cutting plate of the first kind differs from the cutting plate of the second kind by an overall geometry, by a dimension of the at least one cutting edge, and by a shape of the at least one cutting edge.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of international patent applicationPCT/EP2016/070452, filed on Aug. 31, 2016 designating the U.S., whichinternational patent application has been published in German languageand claims priority from German patent application DE 10 2015 115 310.6,filed on Sep. 10, 2015. The entire contents of these priorityapplications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

This disclosure relates to a whirling tool for machining a workpiece.This disclosure relates in particular to a whirling tool havingreplaceable cutting plates. This whirling tool is suitable in particularfor thread whirling.

Whirling is a metal-cutting manufacturing method which in terms of thetool and in terms of the kinetics represents a special form of screwmilling. Whirling serves in particular for producing threads, howevercan also be generally used for producing rotationally symmetrical partssuch as, for example, worms, screws, or rotors.

By virtue of the high performance capability of this metal-cuttingmanufacturing method, whirling is suitable in particular for machiningworkpieces from tough materials such as titanium or precious metal. Forthis reason, the majority of all bone screws today are produced bythread whirling, for example.

It is a characteristic of whirling that both the whirling tool as wellas the workpiece are rotated. The whirling tool which determines thecutting speed, orbits in an eccentrically positioned manner at a highrotational speed about the slowly rotating workpiece. The feed rate ofthe workpiece along the longitudinal axis of the latter is set accordingto the desired thread pitch to be produced. Moreover, the whirling tool,depending on the desired thread pitch, is pivoted about the x-axis ofsaid whirling tool. The radial infeed of the whirling tool in relationto the workpiece establishes the depth of the thread.

By virtue of the eccentric positioning of the workpiece in relation tothe whirling tool, relatively short chips are formed. This has anadvantageous effect on the surface quality of the machined workpiece.

A difference is made between external whirling and internal whirling.External whirling typically serves for producing external threads,whereas internal whirling typically serves for producing internalthreads. The cutting edges in the case of external whirling are directedinward, wherein the whirling tool rotates about the workpiece.Therefore, external whirling is in some instances also referred to asmilling by milling cutting edges with internal teeth. In contrast, thecutting edges in the case of internal whirling are directed outward. Thewhirling tool herein rotates within a bore of the workpiece. Theprinciple of the eccentric whirling movement of the tool and of thesimultaneous movement of the workpiece (both rotating as well as in thelongitudinal direction) in the case of external and internal whirling isotherwise identical.

A problem which can be determined in the case of whirling tools is therelatively high wear on the used cutters or cutting edges, respectively.This in many instances leads to relatively short service lives. Thecutting plates have to be replaced often in the case of whirling toolshaving replaceable cutting plates. This in turn ultimately leads toincreased production costs.

SUMMARY OF THE INVENTION

It is an object to provide a whirling tool for machining a workpiece, inwhich the wear on the cutting edges used is reduced such that theservice lives can be increased.

In view of this object, a whirling tool for machining a workpiece ispresented, having;

-   -   three cutting, wherein each of the cutting plates comprises a        cutting edge;    -   a cutting plate holder having three cutting plate receptacles,        wherein each of the cutting plate receptacles is configured to        receive one of the cutting plates, wherein the cutting plate        receptacles are disposed so as to be distributed in a        circumferential direction across the cutting plate holder; and    -   three fastening elements, wherein each of the three fastening        elements is configured to fasten one of the cutting plates in        one of the cutting plate receptacles of the cutting plate        holder;

wherein the three cutting plates are disposed beside one another on thecutting plate holder, form a first group of cutting plates, and comprisetwo cutting plates of a first kind and one cutting plate of a secondkind, wherein a first one of the two cutting plates of the first kind isdisposed on the cutting plate holder between a second one of the twocutting plates of the first kind and the cutting plate of the secondkind, wherein the two cutting plates of the first kind differ from thecutting plate of the second kind by an overall geometry and by a shapeof the cutting edge.

According to a refinement, the whirling tool comprises a second group ofcutting plates comprising three further cutting plates which aredisposed beside one another on the cutting plate holder in three furthercutting plate receptacles and fastened to the cutting plate holder bythree further fastening elements, wherein said second group of cuttingplates comprises two cutting plates of the first kind and one cuttingplate of the second kind, wherein a first one of the two cutting platesof the first kind of said second group is disposed on the cutting plateholder between a second one of the two cutting plates of the first kindof said second group and the cutting plate of the second kind of saidsecond group, and wherein the cutting plate of the second kind of saidsecond group is arranged on the cutting plate holder beside the secondone of the two cutting plates of the first kind of said first group.

According to a further refinement, the whirling tool comprises sixfurther cutting plates which are disposed beside one another on thecutting plate holder in six further cutting plate receptacles, andfastened to the cutting plate holder by six further fastening elements,wherein three of said six further cutting plates form a second group ofcutting plates and the other three of said six further cutting platesform a third group of cutting plates, wherein each of said second andthird group of cutting plates comprises two cutting plates of the firstkind and one cutting plate of the second kind, wherein a first one ofthe two cutting plates of the first kind of said second group isdisposed on the cutting plate holder between a second one of the twocutting plates of the first kind of said second group and the cuttingplate of the second kind of said second group, wherein a first one ofthe two cutting plates of the first kind of said third group is disposedon the cutting plate holder between a second one of the two cuttingplates of the first kind of said third group and the cutting plate ofthe second kind of said third group, wherein the cutting plate of thesecond kind of said second group is arranged on the cutting plate holderbeside the second one of the two cutting plates of the first kind ofsaid first group, and wherein the cutting plate of the second kind ofthird group is arranged on the cutting plate holder beside the secondone of the two cutting plates of the first kind of said second group.

According to a still further refinement, the cutting plate of the secondkind of said first second group is arranged on the cutting plate holderbeside the second one of the two cutting plates of the first kind ofsaid third group

In other words, the whirling tool comprises:

-   -   three or a multiple of three cutting plates, wherein each of the        cutting plates comprises at least one cutting edge;    -   a cutting plate holder having a plurality of cutting plate        receptacles, wherein each of the cutting plate receptacles is        configured to receive one of the cutting plates, wherein the        cutting plate receptacles are disposed so as to be distributed        in a circumferential direction across the cutting plate holder;        and a plurality of fastening elements for releasably fastening        the cutting plates in the cutting plate receptacles of the        cutting plate holder;

wherein the cutting plates comprise two different kinds of cuttingplates, wherein each group of three of the cutting plates that aredisposed beside one another on the cutting plate holder comprises twocutting plates of a first kind and one cutting plate of a second kind,wherein one of the two cutting plates of the first kind is disposed onthe cutting plate holder between the other one of the two cutting platesof the first kind and the cutting plate of the second kind, wherein thetwo cutting plates of the first kind differ from the cutting plate ofthe second kind by an overall geometry, by a dimension of the at leastone cutting edge, and by a shape of the at least one cutting edge.

The whirling tool according to the disclosure comprises three cuttingplates or a multiple of three cutting plates. The tool particularlypreferably comprises precisely 6, precisely 9, or precisely twelvecutting plates. These cutting plates are attached so as to bereplaceable on a cutting plate holder. The cutting plates are disposedso as to be distributed in the circumferential direction on the cuttingplate holder and are preferably mutually spaced apart. A particularlycharacteristic feature of the whirling tool according to the disclosureis the use of at least two different kinds of cutting plates whichdiffer either in the overall geometry (dimension and/or shape) thereof,and/or in the dimension and/or shape of the cutting edges. It is inparticular provided according to the disclosure herein that for eachgroup of three cutting plates that are disposed beside one another onthe cutting plate holder at least one cutting plate of the first kindand one cutting plate of the second kind are used.

The term “cutting plates disposed beside one another on the cuttingplate holder” is presently to be understood to mean cutting plates whichin the assembled state of the whirling tool are directly sequential whenviewed in the circumferential direction. “Directly” herein is not toimply that the cutting plates that in the circumferential direction aresequential have to contact one another. Cutting plates that are disposedbeside one another can in principle indeed be in mutual contact,however, said cutting plates are preferably mutually spaced apart. Inother words, “cutting plates that are disposed beside one another” arepresently understood to mean such cutting plates which are disposed soas to be direct neighbors to one another on the cutting plate holder. Interms of the whirling tool according to the disclosure which comprisesthree or a multiple of three cutting plates, this thus means that eachof the cutting plates together with its two neighboring cutting plates(left and right) form one group of three cutting plates, of which atleast one cutting plate is a cutting plate of the first kind and onecutting plate is a cutting plate of the second kind.

The use of different kinds of cutting plates has proven advantageous inparticular in terms of the overall wear thereon. By virtue of thedifferent overall geometries, or of the different geometries of thecutting edges, respectively, the cutting plates of the first kind in themachining of the workpiece assume another function than the cuttingplates of the second kind. The cutting plates of the second kind, forexample due to the shape thereof, can be conceived for the preliminarycutting or roughing, respectively, while the cutting plates of the firstkind have contour-imparting cutting edges which are responsible for theproduction of the final threaded profile. In this way, the cuttingplates of the second kind are stressed in a comparatively heavy mannerand subtract a relatively large quantity of material, whereas thecutting plates of the first kind are stressed to a lesser extent andform “only” the details of the contour that is to be represented on theworkpiece. This indeed leads to an overall situation in which thecutting plates of the second kind wear more rapidly when compared to thecutting plates of the first kind. This, however, is acceptable, indeedeven advantageous, since the ultimately contour-imparting cutting edgesof the cutting plates of the first kind are subject to less wear. Insuch a case, an at least partially worn-out cutting edge of the cuttingplates of the second kind can in some instances even remain undetected(as long as the cutting edges of the cutting plates of the first kindare not also worn-out), since the former has no or only a very minoreffect on the surface quality on the workpiece.

It is particularly preferable herein that the cutting plates of thefirst kind and the cutting plates of the second kind are not alwaysdisposed in an alternating manner on the cutting plate holder, but thateach cutting plate of the first kind is disposed on the cutting plateholder between one other cutting plate of the first kind and one cuttingplate of the second kind. If the cutting plates of the first kind forthe sake of simplicity are referred to as “A” and the cutting plates ofthe second kind as “B”, the following arrangement on the cutting plateholder thus results: AABAAB . . . (When viewed sequentially in thecircumferential direction).

Following the example above, that the cutting plates of the second kindare used for preliminary cutting, subtracting material, or roughing,respectively, and the cutting plates of the first kind are used forproducing the threaded profile, in the case of the last-mentionedrefinement one of three cutting plates assume in each case the task ofroughing or material subtraction, respectively, and two of three cuttingplates assume the production of the final threaded profile. A cuttingplate of the first kind which in the machining of the workpiece in thecircumferential direction and thus also in the rotation direction of thewhirling tool contacts the workpiece after a cutting plate of the secondkind and after one other cutting plate of the first kind is thereforestressed to a relatively minor extent.

According to a further refinement, each cutting plate has one main bodyand at least one cutting body which is integrally connected to the mainbody and which projects from the main body and on which the at least onecutting edge of the cutting plate is disposed, wherein the respective atleast one cutting body of the cutting plates of the first kind has alarger volume than the respective at least one cutting body of thecutting plates of the second kind.

Both the cutting plates of the first kind, as well as the cutting platesof the second kind, preferably each have two cutting bodies which aredisposed on opposite ends of the main body. The two cutting bodies ofthe cutting plates of the first kind are preferably identical. Likewise,the cutting bodies of the cutting plates of the second kind arepreferably identical. The cutting bodies differ only among one another(first kind differing from the second kind), as mentioned. This resultsin that both the cutting plates of the first kind, as well as thecutting plates of the second kind, can be released from the cuttingplate holder and can be reattached rotated by 180° to the cutting plateholder, without this changing the functional mode of the whirling tooldescribed above.

While the principle mentioned above is capable of being used generallyboth in the case of external whirling tools as well as in the case ofinternal whirling tools, said principle in tests to date by theapplicant has demonstrated to be particularly advantageous in particularin the case of external whirling tools. Accordingly, the cutting plateholder according to a refinement has a central through hole throughwhich the workpiece during machining is guidable, wherein the cuttingplates in the assembled state of the whirling tool project into thepassage opening. each of the cutting plates (irrespective of the kind)projects into the passage opening by way of one cutting body of thepreferably two cutting bodies of said cutting plates.

In a further refinement, the passage opening is designed so as to besymmetrical in relation to a longitudinal axis of the whirling tool,wherein the respective at least one cutting edge of the cutting platesof the first kind in the assembled state of the whirling tool projectfurther into the passage opening and have a smaller spacing from thelongitudinal axis than the respective at least one cutting edge of thecutting plates of the second kind.

This leads to the situation already described, that the cutting platesof the first kind generate the details of the contour on the workpiece,and the cutting plates of the second kind are used for the preliminarycutting of the threaded profile. Therefore, the at least one cuttingedge of the cutting plate of the first kind preferably has a moremultifaceted contour than the respective at least one cutting edge ofthe cutting plates of the second kind. A “more multifaceted contour” ispresently understood to be a contour of the cutting edge which, inrelative terms, has a larger number of different curvatures or bends.Alternatively, it could also be said that the respective at least onecutting edge of the cutting plates of the first kind is preferablyrather curved, and the respective at least one cutting edge of thecutting plates of the second kind is preferably rather linear orangular.

According to a further refinement, the cutting plate holder when viewedin the plan view along the longitudinal axis is substantially toroidal.The cutting plate holder can therefore be inserted into a substantiallycylindrical main holder which is capable of being coupled to a tooldriving spindle.

According to a further refinement, the respective at least one cuttingbody of the cutting plates of the first kind at a frontal end which inthe assembled state of the whirling tool projects into the passageopening has a smaller height than the respective at least one cuttingbody of the cutting plates of the second kind, wherein the height ismeasured parallel with the longitudinal axis of the whirling tool. Thisadditionally de-stresses the cutting plates of the first kind, onaccount of which the wear on the latter is reduced.

According to a further refinement, each of the cutting plate receptacleshas a planar bearing face which runs so as to be transverse, preferablyorthogonal, to the longitudinal axis of the whirling tool, and twomutually spaced apart bearing faces which run so as to be orthogonal tothe bearing face, the normal vectors of said contact faces enclosing anacute angle. On account thereof, a stable plate seat results for each ofthe cutting plates that are disposed in the cutting plate holder.

According to a further preferred refinement, the fastening elements haveclamp screws which engage in respective threads which are provided inthe cutting plate holder, wherein the central axes of the threads areall spaced so as to be equidistant from the central longitudinal axis ofthe whirling tool. The centers of the threads lie on a common circle, soto speak.

It is to be understood that the features mentioned above and yet to beexplained hereunder are capable to be used not only in the combinationstated in each case, but also in other combinations or individually,without departing from the spirit and scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of an exemplary embodiment of thewhirling tool;

FIG. 2 shows a plan view from above of the exemplary embodiment of thewhirling tool shown in FIG. 1;

FIG. 3 shows a detailed view of the exemplary embodiment of the whirlingtool shown in FIG. 1;

FIG. 4 shows a perspective view of a cutting plate holder of thewhirling tool according to the exemplary embodiment shown in FIG. 1;

FIG. 5 shows a plan view from above of the cutting plate holder shown inFIG. 4;

FIG. 6 shows an exemplary embodiment of a cutting plate of a first kind,used in the whirling tool; and

FIG. 7 shows an exemplary embodiment of a cutting plate of a secondkind, used in the whirling tool.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1 to 3 show an exemplary embodiment of the whirling tool in aperspective view, in a plan view from above, and in a detailed view. Thewhirling tool therein, in its entirety, is identified by the referencesign 10.

The whirling tool 10 comprises a cutting plate holder 12 on which aplurality of cutting plates 14 a, 14 b are releasably fastened with theaid of fastening elements 16. The cutting plates 14 a, 14 b arepreferably reversible cutting plates from hard metal. The fasteningelements 16 are preferably implemented as clamp screws which engage inrespective threads 18 which are provided in the cutting plate holder 12(cf. FIGS. 4 and 5). The clamp screws 16 are preferably provided with aTorx tool engagement or a hexagonal socket tool engagement, while inprinciple any kinds of tool engagements can be considered. The cuttingplate holder 12 is preferably produced from steel. Said cutting plateholder 12 can be constructed so as to be integral (from a singleintegral component) or in multiple parts (from a plurality ofinterconnected components).

The whirling tool 10 according to the exemplary embodiment shown herehas a total of nine cutting plates 14 a, 14 b which are disposed so asto be disposed in the circumferential direction 20 on the cutting plateholder 12. In alternative exemplary embodiments of the whirling tool 10,for example 3, 6, or 12 cutting plates 14 a, 14 b can also be providedinstead of nine cutting plates 14 a, 14 b, without departing from thespirit and scope of the present disclosure.

The whirling tool 10 in the exemplary embodiment shown is embodied as anexternal whirling tool. External whirling tools of this kind serve inparticular for producing external threads.

The whirling tool 10 is usually driven at relatively high rotationalspeeds in the circumferential direction 20. In order for the cuttingplane of the tool cutting edges to be set, or in order for the threadpitch to be set, respectively, the cutting plate holder 12 during therotation thereof is tilted relative to the workpiece by a desired angleabout the x-axis of said cutting plate holder 12. The workpiece (notillustrated) likewise rotates about the longitudinal axis thereof,however at a substantially lower rotational speed than the whirling tool10. During machining, the workpiece is pushed along the longitudinaldirection thereof through the passage opening 22 that is provided so asto be central in the cutting plate holder 12. However, the workpieceduring this feed movement is not positioned in a centric, but aneccentric or out-of-center manner, respectively, in the passage opening22 of the whirling tool 10. The kinematics typical of whirling resultson account thereof. By virtue of the eccentric and tilted arrangement ofthe whirling tool 10 relative to the workpiece, it is in particulartypical herein that, as opposed to circular milling, for example, notall cutting plates 14 a, 14 b engage simultaneously on the workpiece butonly some or even only one of the cutting plates 14 a 14 b engage on theworkpiece at any momentary point in time. The cutting plates 14 a, 14 bthus contact the workpiece in a temporally sequential manner.

In a manner typical for such an external whirling tool, the cuttingplate holder 12 for the aforementioned reasons therefore has a centralthrough hole 22 through which the workpiece is guidable duringmachining. This passage opening 22 is preferably symmetrical to thelongitudinal axis 24 of the whirling tool 10. The passage opening 22 inthe present exemplary embodiment is designed so as to be cylindrical.However, this is not mandatory. Other shapes are also conceivable inprinciple. However, the cutting plate holder 12 is not necessarilysymmetrical to the longitudinal axis 24, as can also be derived from theexemplary embodiment illustrated.

Each of the cutting plates 14 a, 14 b is disposed individually incutting plate receptacles 26 that are provided therefor on the cuttingplate holder 12. Each of these cutting plate receptacles 26 has a planarbearing face 28 and two mutually spaced apart contact faces 30, 32 (cf.FIGS. 4 and 5). The bearing faces 28 of the individual cutting platereceptacles 26 preferably transition into one another, as can be seenfrom FIGS. 4 and 5. Said bearing faces 28 are thus aligned so as to bemutually coplanar and preferably so as to be orthogonal to thelongitudinal axis 24 of the whirling tool 10. The two contact faces 30,32, however, are aligned so as to be preferably parallel with thelongitudinal axis 24, thus orthogonal to the bearing face 28. The twocontact faces 30, 32 of each cutting plate receptacle 26 in theexemplary embodiment shown are mutually aligned at an acute angle. Thisenables a stable seat of the cutting plates 14 a, 14 b in the cuttingplate receptacles 26.

The cutting plates 14, 14 b in the assembled state of the whirling tool10 project into the passage opening 22 of the cutting plate holder 12(cf. in particular FIG. 2). Since not only cutting plates of a singletype, but cutting plates 14 a, 14 b of at least two different types areused, said cutting plates 14 a, 14 b project dissimilarly far into thepassage opening 22 of the cutting plate holder 12. Different orbits 34,36 of the cutting plates 14 a, 14 b, or of the cutting edges of thelatter, respectively, result therefrom.

Two different kinds of cutting plates are used in the present exemplaryembodiment, one cutting plate 14 a of a first kind, or of a first type,respectively (cf. FIG. 6 for details), and one cutting plate 14 b of asecond kind, or of a second type, respectively (cf. FIG. 7 for details).

The two different kinds of cutting plates 14 a, 14 b differ from oneanother by the overall geometry thereof (dimensional and/or shape) andby the dimension and/or shape of the cutting edges thereof. Said cuttingplates 14 a, 14 b thus also differ in terms of the function thereof. Thecutting plates 14 a of the first kind are used in particular forimparting the contour, or for finishing the threaded profile to beproduced. In contrast, the cutting plates 14 b of the second kind aremainly used for roughing (subtracting material), or for the preliminarycutting of the threaded profile to be produced, respectively.

Both cutting plate types 14 a, 14 b have a main body 38 a or 38 b,respectively, and two cutting bodies 40 a or 40 b, respectively, whichproject from the main body 38 a or 38 b, respectively, and which areintegrally connected to the latter. The main body 38 a of the cuttingplates 14 a of the first kind does not differ at all or only to a minorextent (at the transition toward the cutting bodies) from the main body38 b of the cutting plates 14 b of the second kind. The substantialdifference between the two cutting plate types 14 a, 14 b lies in thedifferent embodiment of the cutting body 40 a, 40 b.

The cutting bodies 40 a of the cutting plates 14 a of the first kind arepreferably designed so as to be larger than the cutting bodies 40 b ofthe cutting plates 14 b of the second kind, or have a larger volume thanthe latter, respectively. The cutting bodies 40 a of the cutting plates14 a of the first kind are mainly designed so as to be deeper than thecutting bodies 40 b of the cutting plates 14 b of the second kind. Theterm “deeper” is presently to be understood that the frontal end of thecutting bodies 40 a of the cutting plates 14 a of the first kind have alarger spacing from the main body 38 a than the frontal end of thecutting body 40 b of the cutting plates 14 b of the second kind.Therefore, the cutting edges 42 a of the cutting plates 14 a of thefirst kind in the assembled state of the whirling tool 10 projectfurther into the passage opening 22 of the cutting plate holder 12 thanthe cutting plates 14 b of the second kind (cf. FIG. 2). The orbit 34 ofthe cutting edges 42 a of the cutting plates 14 a is therefore smaller,that is to say has a smaller diameter, than the orbit 36 of the cuttingplates 14 b. Instead, the cutting bodies 40 b of the cutting plates 14 bof the second kind in particular in the region of the frontal end of thecutting body 40 b are designed so as to be higher than the cuttingbodies 40 a of the cutting plates 14 a of the first kind. The height ofthe cutting plates 14 a, 14 b, or of the cutting bodies 40 a, 40 bthereof, respectively, is understood to be the dimension of said cuttingplates or cutting bodies which in the installed state is measuredparallel with the longitudinal axis 24.

The cutting plates 14 a, 14 b are preferably not always disposed in analternating manner on the cutting plate holder 12, but in (imaginary)groups of three cutting plates, wherein each group of three cuttingplates comprises two cutting plates 14 a of the first kind and onecutting plate 14 b of the second kind. In other words, each cuttingplate 14 a of the first kind is disposed on the cutting plate holder 12between one other cutting plate 14 a of the first kind and one cuttingplate 14 b of the second kind. The cutting plates 14 b of the secondkind thus cut the threaded segments in a preliminary manner, and the twocutting plates 14 a of the first kind that directly follow in therotation direction 20 of the whirling tool 10 complete the cutting ofthe threaded segments and finish the threaded profile. In particularthat cutting plate 14 a that is the next but one to follow each cuttingplate 14 b in the rotation direction 20 is stressed the least, onaccount thereof. The wear on said cutting plate 14 a is thus less thanthe wear on the cutting plates 14 b. However, since said cutting plates14 a impart the actual contour of the thread to be produced, relativelypositive machining results can still be achieved also in the case ofwear on the cutting plates 14 b and on the cutting plates 14 a that inthe rotation direction 20 directly follow the cutting plates 14 b. Anywear on the cutting plates 14 b and on the cutting plates 14 a that inthe rotation direction 20 directly follow the latter can therefore bereadily accepted without this leading to the surface quality on thethread to be produced being perceivably compromised. An overall greaterservice life of all cutting plates 14 a, 14 b can thus be implemented.

It is finally to be noted that the principle of a plurality of differentkinds of cutting plates as described above is also capable of being usedin the case of an internal whirling tool. Instead of cutting plates 14a, 14 b having in each case two cutting bodies 42 a, 42 b (so-calleddual cutters), cutting plates having only one cutting body (so-calledsingle cutters) or having more than two cutting bodies (for example,triple cutters or quadruple cutters) can also be used in principlewithout departing from the spirit and scope of the present disclosure.In principle, three different kinds of cutting plates can also be used.The geometric embodiment of the individual cutting edges 42 a, 42 b islikewise not restricted to the shape shown in the figures.

1-14. (canceled)
 15. A whirling tool for machining a workpiece, having:a first cutting plate comprising a first cutting edge; a second cuttingplate comprising a second cutting edge; a third cutting plate comprisinga third cutting edge; a fourth cutting plate comprising a fourth cuttingedge; a fifth cutting plate comprising a fifth cutting edge; a sixthcutting plate comprising a sixth cutting edge; and a cutting plateholder having six cutting plate receptacles which are disposed so as tobe distributed in a circumferential direction across the cutting plateholder, wherein each of the six cutting plates is arranged in one of thesix cutting plate receptacles, the six cutting plates being arranged inascending order from the first to the sixth cutting plate in thecircumferential direction next to one another on the cutting plateholder, wherein the second cutting plate, the third cutting plate, thefifth cutting plate, and the sixth cutting plate are cutting plates of afirst kind, and wherein the first cutting plate and the fourth cuttingplate are cutting plates of a second kind, the cutting plates of thefirst kind being different from the cutting plates of the second kind byan overall geometry and by a shape of their cutting edges.
 16. Thewhirling tool as claimed in claim 15, comprising six fastening elements,wherein each of the first to the sixth cutting plate is fastened in oneof the six cutting plate receptacles by means of one of the sixfastening elements.
 17. The whirling tool as claimed in claim 16,wherein the cutting plate holder comprises six threads, wherein each ofthe six threads is arranged in one of the six cutting plate receptacles,respectively, the six threads being arranged equidistant from a centrallongitudinal axis of the whirling tool.
 18. The whirling tool as claimedin claim 15, wherein each of the cutting plates of the first kindcomprises a first main body and a first cutting body which is integrallyconnected to the first main body and projects therefrom, and whereineach of the cutting plates of the second kind comprises a second mainbody and a second cutting body which is integrally connected to thesecond main body and projects therefrom, the first cutting body having alarger volume than the second cutting body.
 19. The whirling tool asclaimed in claim 15, wherein the cutting plate holder has a centralthrough hole, wherein each of the six cutting plates projects into thethrough hole.
 20. The whirling tool as claimed in claim 19, wherein thethrough hole is symmetrical with respect to a central longitudinal axisof the whirling tool, and wherein each of the second cutting plate, thethird cutting plate, the fifth cutting plate, and the sixth cuttingplate projects farther into the through hole and has a smaller distancefrom the central longitudinal axis than each of the first cutting plateand the fourth cutting plate.
 21. The whirling tool as claimed in claim20, wherein each of the second cutting plate, the third cutting plate,the fifth cutting plate, and the sixth cutting plate at a frontal endwhich in the assembled state of the whirling tool projects into thethrough hole has a smaller height than each of the first cutting plateand the fourth cutting plate, said height being measured parallel to thecentral longitudinal axis.
 22. The whirling tool as claimed in claim 20,wherein each of the six cutting plate receptacles has a planar bearingface which runs transverse to the central longitudinal axis of thewhirling tool, and two mutually spaced apart contact faces which runorthogonal to the bearing face, said contact faces enclosing an acuteangle.
 23. The whirling tool as claimed in claim 15, wherein the cuttingplate holder is toroidal.
 24. The whirling tool as claimed in claim 15,wherein each of the second cutting edge, the third cutting edge, thefifth cutting edge, and the sixth cutting edge has a first contour, andwherein each of the first cutting edge and the fourth cutting edge has asecond contour that is more multifaceted than the first contour.
 25. Thewhirling tool as claimed in claim 15, wherein each of the second cuttingedge, the third cutting edge, the fifth cutting edge, and the sixthcutting edge is curved, and wherein each of the first cutting edge andthe fourth cutting edge is linear or angular.
 26. The whirling tool asclaimed in claim 15, wherein the cutting plates are precisely sixcutting plates, and wherein the sixth cutting plate is arranged next tothe first cutting plate in the circumferential direction.
 27. A whirlingtool for machining a workpiece, having: precisely three cutting plates,namely a first cutting plate comprising a first cutting edge, a secondcutting plate comprising a second cutting edge, and a third cuttingplate comprising a third cutting edge; and a cutting plate holder havingthree cutting plate receptacles which are disposed so as to bedistributed in a circumferential direction across the cutting plateholder, wherein each of the three cutting plates is arranged in one ofthe three cutting plate receptacles, the three cutting plates beingarranged in ascending order from the first to the third cutting plate inthe circumferential direction next to one another on the cutting plateholder, wherein the second cutting plate and the third cutting plate arecutting plates of a first kind, and wherein the first cutting plate iscutting plate of a second kind, the cutting plate of the first kindbeing different from the cutting plates of the second kind by an overallgeometry and by a shape of their cutting edges.
 28. The whirling tool asclaimed in claim 27, comprising three fastening elements, wherein eachof the first to the third cutting plate is fastened in one of the threecutting plate receptacles by means of one of the three fasteningelements.
 29. The whirling tool as claimed in claim 28, wherein thecutting plate holder comprises three threads, wherein each of the threethreads is arranged in one of the three cutting plate receptacles,respectively, the three threads being arranged equidistant from acentral longitudinal axis of the whirling tool.
 30. The whirling tool asclaimed in claim 27, wherein the cutting plate holder has a centralthrough hole, wherein each of the three cutting plates projects into thethrough hole.
 31. The whirling tool as claimed in claim 30, wherein thethrough hole is symmetrical with respect to a central longitudinal axisof the whirling tool, and wherein each of the second cutting plate andthe third cutting plate projects farther into the through hole and has asmaller distance from the central longitudinal axis than the firstcutting plate.
 32. The whirling tool as claimed in claim 31, whereineach of the second cutting plate and the third cutting plate at afrontal end which in the assembled state of the whirling tool projectsinto the through hole has a smaller height than the first cutting plate,said height being measured parallel to the central longitudinal axis.33. The whirling tool as claimed in claim 27, wherein each of the secondcutting edge and the third cutting edge has a first contour, and whereinthe first cutting edge has a second contour that is more multifacetedthan the first contour.
 34. The whirling tool as claimed in claim 27,wherein each of the second cutting edge and the third cutting edge iscurved, and wherein the first cutting edge is linear or angular.